EPA's Vessel General Permit and Small Vessel General

Southern Hemisphere. Humpback whales are abundant throughout the Antarctic during the
summer; they occur south to the ice edge but not within the pack ice zone (Reilly et al. 2008). In
the winter, Southern Hemisphere whales migrate to coastal areas within the South Pacific, South
Atlantic, and Indian Oceans. There is genetic differentiation within and among all southern
ocean basins (Baker et al. 1998, Rosenbaum et al. 2009). Over 200,000 humpback whales were
killed in the Southern Hemisphere during the early 20 th century. The area now supports more
than 36,000 humpback whales and is growing at a minimum annual rate of 4.6 percent (Reilly et
al. 2008)
Arabian Sea. A small, genetically and demographically distinct population of humpback whales
resides year-round in the Arabian Sea (Mikhalev 1997, Reilly et al. 2008). Though historical
estimates are not available, 242 whales were killed in 1965 and 1966 (Reilly et al. 2008). The
minimum population size, based on photo-identification data, is 56 whales (Mikhalev 1997); the
maximum estimate is 400 (Reilly et al. 2008).
Threats
Three human activities are known to threaten humpback whales: directed harvest, fisheries
interactions, and vessel collisions. Historically, whaling represented the greatest threat to every
population of humpback whales. It was ultimately responsible for the global decline in
humpback whales prior to their listing as an endangered species. Hundreds of thousands of
whales were removed from the world’s oceans prior to bans on commercial whaling in the mid-
20 th century (Reilly et al. 2008). Humpback whales are often killed or injured during interactions
with commercial fishing gear. They are vulnerable to ship strikes, which are often fatal. Their
natural predators my include orcas, false killer whales, and sharks.
Life History Information
Humpback whale reproductive activities occur primarily in winter. Gestation takes about 11
months (Winn and Reichley. 1985), followed by a nursing period of up to one year (Baraff and
Weinrich 1993). Calving occurs in the shallow coastal waters of continental shelves and some
oceanic islands (Perry et al. 1999). The calving interval is likely two to three years (Clapham
and Mayo 1987), although some evidence exists of calving in consecutive years (Glockner-
Ferrari and Ferrari 1985, Clapham and Mayo 1987, 1990, Weinrich et al. 1993). Mother/calf
groups are found in relatively stable pairs (Ersts and Rosenbaum 2003). Sexual maturity in
humpback whales is reached between five and 11 years of age (Clapham 1992, Gabriele et al.
2007). During the breeding season, humpback whales form small unstable groups (Clapham
1996). Males sing long, complex songs, compete for mates, and are polygamous (Clapham
1996).
Humpback whales migrate long distances from breeding areas to foraging areas. Although
largely solitary, humpback whales often cooperate during feeding activities (Elena et al. 2002).
Feeding groups are sometimes stable for long periods of times, and there is good evidence of
some territoriality on both feeding (Clapham 1996) and wintering grounds (Tyack 1981).
Humpbacks exhibit a wide range of foraging behaviors and feed on a range of prey types,
including: small schooling fishes, euphausiids, and other large zooplankton (Nemoto 1957,
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